Chaka Khan, Dawn Upshaw, Shawn Colvin, Jonatha Brooke, Karen Carpenter, Yolanda Adams, Whitney Houston, Erana Clark, Ella Fitzgerald... Etc... There is no best.
Hadrien Feraud on the Zawinul song 'Fast City' - on the Scott Kinsey album "We Speak Luniwaz".
Jimmy Johnson on the song 'Pud Wud' on the Allan Holdsworth album "Sand".
John Patitucci on 'Assim Nao Da' on his album "Mistura Fina"
Gary Willis on the song 'It's Only Music' on his album, "Bent"...
If they are of a 'certain age', and are not of the frame of mind that "I want to learn something every day" then there is next to no chance they will change anything because you suggest something to them. I would leave. People don't change (usually)...
Ray Brown and George Mraz with Oscar Peterson, then Marcus Miller on Dave Grusin's Mountain Dance, Havona, Teen Town, then the Bob James album 'One on One' with Neil Jason and Garry King (and Ron Carter), then hundreds more...
I find that a different part of your brain is used when you use a computer versus paper and pencil.
Computers immediately fill your head with the other programs you use there, and often with notifications, crashes, need to save, whereas paper has ZERO walls between your mind and the music...
Most people tend to learn what they like, and who they would like to sound similar to.
If you want to learn how to do it it will most likely come from a song you really like the sound of and want to duplicate - 'forget me nots' by Patrice Rushen for e.g. or some of the playing on Anita Baker's...